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RAeS General Aviation Group
Light Aircraft Design Conference Methods and Tools
16th November 2015
Using Simulators in the Design Process Dr. M. Jump, Dr. M.D. White
@drmikejump
Introductions
• Dr. M. Jump
• BEng Aeronautical Engineering, University of Bristol 1994
• Aerodynamicist BAE Systems
• PhD (Pilot Guidance Displays), University of Liverpool, 2007
• Lecturer 2007 – 2014, Senior Lecturer 2014 – date, Aerospace Engineering
• PPL since 1997
• Studying/training for IMC
Aircraft Design at UoL
• Aircraft Design and Aerospace Capstone Project to provide aircraft
design exercises that require the INTEGRATION of knowledge and
skills learned throughout the degree programme.
• Aircraft Design (Year 3, BEng (optional) and MEng (compulsory))
• Learn the tools/methods and techniques to...
• Perform a conceptual design against a requirement
• Aerospace Capstone Design Project (Year 4, MEng and MSc)
• Perform a conceptual design against a requirement and then...
• Perform a detailed analysis of the conceptual design (aerodynamics,
avionics, flight dynamics, structures.....etc.)
• Simulation and simulators used throughout
Aircraft Design – Art and Engineering
“A beautiful aircraft is the expression of the genius of a
great engineer who is also a great artist” Shute N., No Highway, 1947
“Airplane design is the intellectual engineering process of
creating…a flying machine to (1) meet certain
specifications and requirements established by potential
users (or as perceived by the manufacturer) and/or (2)
pioneer innovative, new ideas and technology” Anderson Jr., J.D., Aircraft Performance and Design, 1999
Simulation/Simulator Simulation is the imitation of the operation of a real-world process
or system over time. The act of simulating something first requires
that a model be developed; this model represents the key
characteristics or behaviours of the selected physical or abstract
system or process. The model represents the system, whereas
the simulation represents the operation of the system over time.
Wikipedia
A Simulator is a machine for simulating certain environmental and
other conditions for the purposes of training or experimentation
http://dictionary.reference.com/browse/simulator
“All models are wrong, some are useable”
Design Phases 1. Requirements Capture
a list of expectations that the aircraft must meet
2. Conceptual Design
formally establishes the initial idea
3. Preliminary Design
ultimately answers whether the idea is viable or not
4. Detail Design
converts the preliminary design into something that can be
built and flown. Start of construction of the proof-of-concept
(poc) aircraft
5. Proof-of-concept aircraft construction and design
culminates with the maiden flight of the poc aircraft
Adapted from: Gudmundsson, S., General Aviation Aircraft Design,
Butterworth-Heinemann, 2014
Modelling
• So, before we can do some ‘simulating’ we need a system
model
• 2 examples
• 1 from concept design phase
• 1 from preliminary/detail design phase
• Once we have the models for these, we can exercise them
through time
Modelling 1 – Take-Off Weight Estimation
Personal
Turboprop
Large Commercial
Military Fighter
Small Commercial
Business Jets
WTO
TO
climb
climb
accel
accel
cruise
cruise
loiter
loiter
land
TO
land
W
W.
W
W.
W
W.
W
W.
W
W
W
W
(Cork
e, T.C
., D
esig
n o
f A
ircra
ft)
Modelling 1 – Take-Off Weight Estimation • So, problem boils down to:
• Selecting an appropriate Structure Factor, ‘s’
• Computing or estimating values for each Fuel Fraction
• For example:
• Empirical (Start Up and Take-Off):
• Computed (Cruise):
0.9750.97WW
off-take
cruise
WW
cruise
loiterlnD
L
C
VRange(nm)
(J. J. Lee, MIT Masters Thesis, 2000)
Simulation 1 – Take-Off Weight Estimation • To simulate through time, we can now iterate
• Guess WTO to give an estimated empty weight:
• Run aircraft through mission using fuel fractions:
• Compare with
• Modify appropriate and repeat until
• This is amenable to a spreadsheet analysis
guessTOempty' WsW
guessTO
climb
climb
accel
accel
cruise
cruise
loiter
loiter
land
guessTO
land
W
W.
W
W.
W
W.
W
W.
W
W
W
W
landTOempty'' WWW
guess
empty''
empty' WW
empty''W
guessTOW
empty'W
Simulation 1 – Take-Off Weight Estimation
Input
Data Initial WTO guess
First
Simulation
W’empty c.f. W’’ empty
Revised WTO guess
Final WTO estimate
Simulation 1 – Take-Off Weight Estimation
• ITERTOW.xls Demo
Modelling 2 – Handling Qualities Analysis • Of course, ‘simulator’ conjures up an image of something more
than a spreadsheet…
Equations
Of
Motion
Aero
Model
Gear
Model
Atmos
Model
Operator
Station
Control
Loading
Data
Acquisition
Engine
Model
Visual
System
Visual
System
Audio
System
Instruments
Nav
Systems
Adapted from: Allerton D., Principles
of Flight Simulation, J. Wiley & Sons,
UK, 2009
Modelling 2 – Handling Qualities Analysis • Need a flight dynamics model…many ways to construct them
Modelling 2 – Handling Qualities Analysis • Each component can be modelled at as high a level of fidelity
as is necessary. What are you trying to achieve?
• Real time or not?
3D
a (rad)
2p Cl, CL
Look-up tables or ‘on-the-fly’ computation?
Simulation 2 – Handling Qualities Analysis • But how can simulators/the simulation model be used?
• To help enable design decisions to mature the design…
• …by rapid prototyping of the vehicle
Simulation 2 – Handling Qualities Analysis • Design modified through the use of a (MATLAB) GUI
• Off-line non-linear analysis re-computed (faster than real-time)
• ‘Better’ response due to increased tail size
Simulation 2 – Handling Qualities Analysis • Once we have the design at our desired level of maturity…
• …we can put a pilot in the loop and go flying, using the same model
• (or you could use a pilot model)
• To ascertain the vehicle’s assigned handling qualities
• To answer design parameter questions
• Etc.
Modelling 2 – Handling Qualities Analysis • Back to what are you trying to achieve?
• HQ example for autogyro
Modelling 2 – Handling Qualities Analysis • Dynamic responses…
Modelling 2 – Handling Qualities Analysis • Re-created a real flight trial in the simulator
Robin
son R
. and J
um
p M
., P
rogre
ss in t
he D
evelo
pm
ent of H
andlin
g Q
ualit
ies C
ritical
Desig
n G
uid
elin
es f
or
an A
uto
gyr
o,
Pro
ceedin
gs o
f th
e A
merican H
elic
opte
r S
ocie
ty
Foru
m, F
oru
m 6
7, V
irgin
ia B
each V
A, 2011.
COTS Flight Simulators for the Designer • There are a number of COTS flight simulators available
• See: McGovern S.M. and Cohen S.B., Survey of contemporary aircraft
fight dynamics models for use in airspace simulation, SPIE 6564,
Modeling and Simulation for Military Operations II, 65640V (10 May
2007); doi: 10.1117/12.719696
• For design purposes, any simulator where you have to tell it how the
vehicle should fly is of little value e.g. using stability derivatives
• One that does not do this is Laminar Research X-Plane (current V10)
• It derives the aerodynamic model from the geometry etc.
COTS Flight Simulators for the Designer
Plane Maker Blade Element
(Momentum)
Theory (BET)
See: http://wiki.x-plane.com/Appendix_A:_How_X-Plane_Works
BET aero are 2D so corrections for: • 2D 3D lift curve slope
• 2D 3D CLmax reduction
• Induced drag correction
• Moment reductions due to AR, taper…
• Compressible flow
• But we know that ‘all models are wrong, some are useable’
• Have mentioned some limitations already (2D etc.)
• Are corrections applied plausible? What are their limitations?
• Others
• Airflow is always in equilibrium, flow adapts instantly to any changes
• Theory breaks down for large deflections e.g. stall
• BUT, if you don’t expect to encounter such conditions, then it may
yield useful results
Other Uses • Other design items that simulators can be useful for:
• Cockpit layout assessment
• Flight control system design
• Avionics assessment
• Human factors studies
• Etc.
• Etc.
Key Points • Simulation is the exercising of a model through time
• Can be used in all phases of design to answer ‘what if’ early in the
process
• Can be used to predict and verify e.g. performance against
requirements
• All models are wrong, some are useable
• Need to understand the capailities and limitations of the model
Acknowledgements • The following contributed in some way to this presentation
material
• Dr. Mark White
• Dr. Sebastian Timme
• Dr. Sophie Robinson
• Mr. Tom Fell
• Mr. Chris Dadswell
• The Aircraft Design and Capstone cohorts from the past few years
ANY QUESTIONS ?
Dr. M. Jump
Flight Science & Technology
The University of Liverpool
